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Types of Radiation

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Types of Radiation

There are 3 types of ionising radiation that you need to be familiar with at Intermediate 2 Physics level.

These are:

  • ALPHA - α - is a helium nucleus, 2 x protons and 2 x neutrons. It has mass and a strong positive charge.
  • BETA - β- is a fast moving electron. It has mass (small) and a negative charge.
  • GAMMA - γ - is a high-energy electromagnetic waves. Gamma rays are caused by changes within the nucleus. They are part of the Electromagnetic Spectrum and so travel at the speed of light. They have no mass and no charge.

Each of the ionising radiations can be defined in terms of their properties in the following areas:

  • Range in air
  • Ionising power
  • Penetrating power
  • Magnetic Field - change of direction

Penetrating Power

Radiation Range in air Ionising Power Can pass through paper? Can pass through 5mm of Aluminium? Can pass through 5cm of Lead? Magnetic field deflection
Alpha 5cm Highly Ionising No No No Deflected towards negative plate
Beta 15cm Ionising Yes No No Deflected toward positive plate
Gamma Much further Weakly ionising Yes Yes Almost all of it is stopped, but some gets through. None

Each type of radiation is caused by a decay of one of two types:

  • Spontaneous - the decay occurs naturally without external interference
  • Induced - the decay has been caused by a reaction

Some atoms are unstable and in an attempt to stabilise the nucleus, the atoms' nucleus undergoes a change. This change may release a form of ionising radiation.

Atoms that do this are said to be radioactive.

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